From the factory on trucks it is about a $1,500 option. I looked into it, and it was VERY expensive-in the thousands to do. If you have the correct linings, balanced drums, automatic slack adjusters, Jake brake, you'll have more then enough brakes. The difference between stopping distances (on a truck) between drum and disc from 60mph is 20ft (course that's the length of a car too). If I were buying a new bus or truck, it would have discs. But retrofitting- $$$$ Good Luck, TomC

Mine were on the bus when I bought it. I have replaced all the pads and done some other things. They stop very smooth and seem trouble freeAll wheels have disk except for the drive wheels. They are still drum.

They are Rockwell's. I discovered that a lot of older emergency vehicles (I.e. Fire ambulance, military) are converted over to after-market disk systems.It seems rather straight forward to me. Everything is bolt-on. This system is much easier to service than my passenger van. I had a leaking rear seal on my driver tag yesterday. I had to pull everything all the way back to the main seal. It only took a few hours and I was just piddling. (If you can call lugging around the 100lb disk hub, to get it in the parts cleaner, piddling ( the calipers weigh at least 75lbs but they just fall into place with two large king pins. One feisty guy can manage. Wish I knew one.All in all, the system might be pricey, I didn't look into that, but it couldn't be more simple.

I would agree with Tom on the fact that a disk system and a drum system are very close in stopping power. I have a 82 MCI with drum. However, that is where the similarities end. The smoothness and ease of stopping are not to be compared. The ease of service is also heavily favoring the disk system. This thing stops like a car.

Very interesting read, my Foretravel has the Meritor disc setup, yes they stop well, they require clay based grease (ONLY) due to heat about every 2 years, can be screwed up very easy, the larger problem is the sticky slide pins, and folks who drive it like a sports car. Some folks with a RV scare me. Can get very costly, burn up rotors, pads and even the calipers. You know the routine about the anvil being destroyed with a feather. The Meritor system is the same as the fire trucks use. There are different models, I do not know the differences between them.Also Foretravel coaches uses the Allison Retarder, it is about 3-4 times more effective than a Jake on a 71 or 92 DDC. It just heats up the radiator going down a long mtn too fast. Common sense is still required.Between the retarder and the disc setup, yes it does stop like a car.Me, being from the trucking world could be just as happy with the drums and retarder.CheersDave M

My slider pins are just sitting exposed in the assembly...., no boots, no grease fittings, no way to oil except rubbing them before you slide them in. Sliding back and forth when you brake cleans them off, I guess.Every time I pull them out they are mirror clean and shiny.Don't know if others are a similar design.

The pins should be free of grease, it tends to have grit etc stuck to it, some use a dry silicone spray.Meritor has a spring kit to help push the pads apart/away from rotor, I do not have it yet.The cost side of the disc brake seems to run from acceptical to real costly, seems to depend on the operator, take a gear head who pays attention to important things, they are in the econ mode. but if your life was sitting at a desk, and head up the butt, things get costly. Like most things I guess.One key seems to be the Clay Based grease, due the the heat, it is used in the screw assy that puts the squeeze on the pads/rotor, it appearently gets hot, above my pay grade, I do not know.Will try to send the Meritor Service Manual for info.Dave M

With all the cost and maintenance issues still with disc brakes, unless a customer wants them, we order all of our trucks with drum brakes. If you have the correct linings, and such, drum brakes will give you many years of faithful service. Except for greasing the pins and slack adjusters, adjusting my brakes once a year, I haven't done anything to my brakes-and they will put you through the windshield (my wife won't want you to know how I know that). Good Luck, TomC